I am having this issue as well. I was using Navis 2016 and am using Fab Cad MEP 2016. I recently purchased the AEC and got Navis Manage with it. I downloaded Navis Manage 2017. It works fine for Navis files that I get from others, I can see all objects, even my own Cad MEP items I have sent to the general contractor to be included in their model. When I try to merge or append my duct into the model, it does not show up. I never had this problem in 2016, but I just opened it and tried it to see if I could keep going while looking for a solution. It is now doing the same thing. I downloaded the 2017 Object enabler, do I need to download the 2016 object enabler since I am using 2016 Cad MEP? Or is it a completely different problem? I really don't want to have to wipe my whole computer and re-download everything.